Filters for straining liquids containing finely dispersed particles therein are commonly formed as a perforated filter basket with a disposable filter element for example made of filter paper inserted into the filter basket. Filters with disposable filter inserts are inconvenient in use, due to the need for always having disposable paper filters available.
The prior art shows filters wherein a screen and a filter frame are combined in various ways. U.S. Pat. No. 4,374,026 shows for example a basket filter with various filter or screen elements having their adjoining edges embedded in plastic. This filter, however, has the drawback that it is composed of several screen parts that must first be assembled and then embedded in plastic. U.S. Pat. No. 4,882,055 shows a unitary injection molded filter wherein the filter screen and the supporting frame are molded as an integral part. This filter, however, has the drawback that a high degree of fineness of the filter is virtually impossible to attain, since every single hole in the filter screen must be molded into the screen during the molding process.
The filter according to U.S. Pat. No. 4,882,055 therefore is unsuitable for filter applications wherein it is necessary to provide a high degree of fineness of the filter screen.
It is accordingly an object of the instant invention to provide a unitary filter assembly that overcomes the drawbacks of the known filters, is inexpensive to manufacture and can be provided with a high degree of fineness of the filter screen.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.